THE TRANSFORMATION FROM GREEN TO CONCRETE CITIES; A REMOTE SENSING PERSPECTIVE
Cities especially in developing countries have been experiencing dramatic transformation as a result of rapid urbanization. For instance, the rate of urbanization in Kenya since independence in 1963 is estimated at 5%. The urban population has risen from 8% at independence to the current figure of 34% (2012). With this trend it is projected that about 50% of the population will be urbanized by the year 2030. The consequence of this is that, cities that were originally regarded as green are gradually being transformed into concrete. This transformation involves largely direct changes in land-use, where areas originally covered by vegetation are now built up. Urban authorities are under increased pressure to cope with the complex dynamics of the demands of the growing population. This paper explores the contribution of Remote Sensing in transformation analysis by proposing a three dimensional approach that endeavours to address the questions regarding to why, what and how. The "why" refers to the drivers of transformation, "what" the consequences thereof whereas "how" focuses on the options the authorities can explore in dealing with the challenges brought about by these changes. Temporal GeoEye images from Google Earth for five epochs namely 2002, 2004, 2007, 2008 and 2012 have been used to show the transformation trend from green to concrete. Upper Hill Area in Nairobi in Kenya has been used to demonstrate this concept and the results obtained have revealed a consistent increase in areas under concrete. Indeed the rate of increase in table 2 shows that there has been additional area under concrete between 2002 and 2004 of 0.39, 2004 and 2007 of 1.15, 2007 and 2008 of 0.74 and, 2008 and 2012 of 1.56.